1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, systems, and products for random access for processing messages in a message queue.
2. Description of Related Art
Message oriented middleware (“MOM”) implements methods of communication between software components or applications. MOM system implement both point-to-point functionality and publish-subscribe functionality. In a point-to-point domain, one source application (a ‘producer’) produces messages for one destination application (a ‘consumer’). Such a MOM system is often envisioned as a peer-to-peer facility in that any client application may function as either a producer or consumer depending on its function at any particular time. In client-server terms, that is, any client can produce or consume messages to or from any other client. Each MOM client typically connects to a messaging agent (sometime called a ‘queue manager’) that provides facilities for creating, sending, receiving, and reading messages.
MOM systems support distributed data communication that is loosely coupled and generally asynchronous. A producer component sends a message to a destination (typically a message queue), and a consumer recipient can retrieve the message from the destination. The producer and the consumer are not required to be available, on-line, or connected to one another for data communications in order to communicate. In fact, the producer does not need to know anything about the consumer, nor does the consumer need to know anything about the producer. The producer and consumer need to know only what message format and what destination (or message queue) to use. In this respect, messaging differs from tightly coupled technologies, such as the Common Object Request Broker Architecture (“CORBA”) or Java's Remote Method Invocation (“RMI”), which require a calling application to know a remote application's methods.
A “message” is a unit of information transmitted electronically from one computer application to another. Examples of messages generally include email messages and messages in data communications protocols such as HTTP or TCP/IP. Many messages in embodiments according to the present invention are units of information communicated in message oriented middleware (“MOM”). MOM messages differ somewhat from many other kinds of messages. Email messages, for example, implement human-readable communications from a person to a person or from a software application to a person. HTTP messages represent requests for particular computer resources and responses to such requests. A MOM messages, however, is used for communications between software applications and other software applications to implement business logic. That is, a MOM message generally communicates input data for, or output data from, operation of some form of business logic, accounting, on-line sales or marketing, financial calculations, security services, and so on.
Examples of MOM systems include IBM's MQSeries products, JMS (the Java Message Service), and MSMQ (Microsoft Message Queuing). MOM systems in prior art typically store messages in queues and support sequential message consumption in modes such as FIFO, LIFO, or according to assigned priorities. In a MOM queue that implements prioritized message consumption, messages having the same priority may be consumed according to a sequential sub-rule such as FIFO or LIFO. With either option, a consumer application may specify a message identification, a unique identifier assigned by a queue manager, and continue reading messages from there. In such systems, however, that implement a point-to-point messaging domain, messages sometimes are often produced for a queue faster than a consumer can consume them, thus creating a processing bottleneck in a queue. There is therefore a continuing need to improvement in such messaging systems.